Hitherto, there has been known an interior permanent magnet motor including a rotor having permanent magnets embedded in a rotor core. In the following description, the interior permanent magnet motor is referred to as “IPM motor”. The IPM motor is capable of obtaining reluctance torque in addition to magnetic torque generated by an attraction force and a repulsion force between a coil and permanent magnets. Therefore, as compared to a surface magnet motor including permanent magnets bonded to an outer peripheral surface of a rotor, the IPM motor achieves higher torque and higher efficiency. As the permanent magnets to be embedded in the rotor core of the IPM motor, there have typically been used sintered magnets such as rare-earth magnets, ferrite magnets, and alnico magnets.
The IPM motor typically includes an annular sensor magnet provided to the rotor, and a rotational position of the rotor is detected through detection of a magnetic force of the sensor magnet with a Hall sensor (Hall element). The sensor magnet described above is fixed to the rotor core, for example, through resin sealing at one end of the rotor core (for example, see Patent Literature 1).